DESCRIPTION: This an application for a NIDA RSDA award. The major focus of my research program is elucidating the cellular effects of cannabinoids (the principal psychoactive constituents of marijuana) in neurons with the aim of understanding the physiology underlying the behavioral actions of these compounds. Cannabinoids, acting at the neuronal cannabinoid receptor (CB-1), are potent modulators of ion channel function. Specifically, they inhibit N-and Q-type voltage-dependent Ca2+ currents and activate an inwardly-rectifying K+ current. These actions suggest that cannabinoids may elicit their behavioral effects by decreasing neuronal excitability and neurotransmitter release from CB-1-expressing neurons. Over the next five years we will extend our studies to the level of synaptic function emphasizing the following projects: l. Investigating if cannabinoids, and an endogenous cannabinoid, anandamide, inhibit neurotransmitter release in neuronal cultures and cell lines using imaging, RIA, and electrophysiological techniques. 2. Determining the G protein alpha subunits mediating cannabinoid receptor-effector coupling and the CB-1 domains important in this coupling. 3. Delineating the role of protein kinase C (PKC) in cannabinoid signaling. Recently we have found that ion channel modulation by cannabinoids is disrupted by PKC activation and that the CB-1 receptor is a PKC substrate. Future studies will determine if CB-1 phosphorylation occurs in situ and if neurotransmitter activation of PKC disrupts cannabinoid-mediated ion channel modulation. 4. Generating CB-l-specific antibodies for affinity purification, labelling and signaling experiments. The projects presented here range from those well within the PI's expertise to those beyond his current training. The rich, collaborative atmosphere at the University of Washington, and the PI's senior colleagues, makes the success of these projects likely. The proposed studies will significantly advance our understanding of the cellular actions of cannabinoids. There are three reasons why this is important: (1) Marijuana use is increasing and is a significant social issue, (2) cannabinoids have therapeutic potential and we need a firm appreciation of their cellular actions to exploit this potential; (3) we know little about the physiological role of endogenous cannabinoids in healthy or diseased brain. Funding of this proposal will permit the investigator sufficient research time to make substantial progress towards elucidating the neuronal basis for the behavioral effects of cannabinoids.